Download or read book SiC Fiber Reinforced Celsian Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-11 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: Celsian is a promising matrix material for fiber-reinforced composites for high temperature structural applications. Processing and fabrication of small diameter multifilament silicon carbide tow reinforced celsian matrix composites are described. Mechanical and microstructural properties of these composites at ambient and elevated temperatures are presented. Effects of high-temperature exposures in air on the mechanical behavior of these composites are also given. The composites show mechanical integrity up to 1100 C but degrade at higher temperatures in oxidizing atmospheres. A model has been proposed for the degradation of these composites in oxidizing atmospheres at high temperatures.Bansal, Narottam P.Glenn Research CenterFABRICATION; MICROSTRUCTURE; SILICON CARBIDES; MECHANICAL PROPERTIES; GLASS; MATRIX MATERIALS; CERAMICS; TEMPERATURE DEPENDENCE; SHEAR STRENGTH; TENSILE STRENGTH; STRESS-STRAIN DIAGRAMS; SCANNING ELECTRON MICROSCOPY; BORON NITRIDES; VAPOR DEPOSITION

Download or read book Effects of Interface Coating and Nitride Enhancing Additive on Properties of Hi Nicalon Sic Fiber Reinforced Reaction Bonded Silicon Nitride Composite written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-27 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: Strong and tough Hi-Nicalon SiC fiber reinforced reaction-bonded silicon nitride matrix composites (SiC/ RBSN) have been fabricated by the fiber lay-up approach. Commercially available uncoated and PBN, PBN/Si-rich PBN, and BN/SiC coated SiC Hi-Nicalon fiber tows were used as reinforcement. The composites contained approximately 24 vol % of aligned 14 micron diameter SiC fibers in a porous RBSN matrix. Both one- and two-dimensional composites were characterized. The effects of interface coating composition, and the nitridation enhancing additive, NiO, on the room temperature physical, tensile, and interfacial shear strength properties of SiC/RBSN matrix composites were evaluated. Results indicate that for all three coated fibers, the thickness of the coatings decreased from the outer periphery to the interior of the tows, and that from 10 to 30 percent of the fibers were not covered with the interface coating. In the uncoated regions, chemical reaction between the NiO additive and the SiC fiber occurs causing degradation of tensile properties of the composites. Among the three interface coating combinations investigated, the BN/SiC coated Hi-Nicalon SiC fiber reinforced RBSN matrix composite showed the least amount of uncoated regions and reasonably uniform interface coating thickness. The matrix cracking stress in SiC/RBSN composites was predicted using a fracture mechanics based crack bridging model. Bhatt, Ramakrishana T. and Hull, David R. and Eldridge, Jeffrey I. and Babuder, Raymond Glenn Research Center NASA/TM-2000-210211, E-12330, NAS 1.15:210211

Download or read book Environmental Effects on the Tensile Strength of Chemically Vapor Deposited Silicon Carbide Fibers written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-16 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The room temperature and elevated temperature tensile strengths of commercially available chemically vapor-deposited (CVD) silicon carbide fibers were measured after 15 min heat treatment to 1600 C in various environments. These environments included oxygen, air, argon and nitrogen at one atmosphere and vacuum at 10/9 atmosphere. Two types of fibers were examined which differed in the SiC content of their carbon-rich coatings. Threshold temperature for fiber strength degradation was observed to be dependent on the as-received fiber-flaw structure, on the environment and on the coating. Fractographic analyses and flexural strength measurements indicate that tensile strength losses were caused by surface degradation. Oxidation of the surface coating is suggested as one possible degradation mechanism. The SiC fibers containing the higher percentage of SiC near the surface of the carbon-rich coating show better strength retention and higher elevated temperature strength. Bhatt, R. T. and Kraitchman, M. D. Glenn Research Center NASA-TM-86981, E-2519, NAS 1.15:86981, USAAVSCOM-TR-85-C-4, AD-A157111 RTOP 533-05-12...

Download or read book Effects of Fiber Content on Mechanical Properties of CVD SiC Fiber Reinforced Strontium Aluminosilicate Glass Ceramic Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-02 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Unidirectional CVD SiC(f)(SCS-6) fiber-reinforced strontium aluminosilicate (SAS) glass-ceramic matrix composites containing various volume fractions, approximately 16 to 40 volume %, of fibers were fabricated by hot pressing at 1400 C for 2 h under 27.6 MPa. Monoclinic celsian, SrAl2Si2O8, was the only crystalline phase formed, with complete absence of the undesired hexacelsian phase, in the matrix. Room temperature mechanical properties were measured in 3-point flexure. The matrix microcracking stress and the ultimate strength increased with increase in fiber volume fraction, reached maximum values for V(sub f) approximately equal to 0.35, and degraded at higher fiber loadings. This degradation in mechanical properties is related to the change in failure mode, from tensile at lower V(sub f) to interlaminar shear at higher fiber contents. The extent of fiber loading did not have noticeable effect on either fiber-matrix debonding stress, or frictional sliding stress at the interface. The applicability of micromechanical models in predicting the mechanical properties of the composites was also examined. The currently available theoretical models do not appear to be useful in predicting the values of the first matrix cracking stress, and the ultimate strength of the SCS-6/SAS composites. Bansal, Narottam P. Glenn Research Center RTOP 505-63-12...

Download or read book Raman Study of Uncoated and P Bn Sic Coated Hi Nicalon Fiber Reinforced Celsian Matrix Composites Part 1 Distribution and Nanostructure of Different written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-26 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hi-Nicalon fiber reinforced celsian matrix composites were characterized by Raman spectroscopy and imaging, using several laser wavelengths. Composite #1 is reinforced by as-received fibers while coatings of p-BN and SiC protect the fibers in composite #2. The matrix contains traces of the hexagonal phase of celsian, which is concentrated in the neighborhood of fibers in composite #1. Some free silicon was evident in the coating of composite #2 which might involve a {BN + SiC yields BNC + Si} "reaction" at the p-BN/SiC interface. Careful analysis of C-C peaks revealed no abnormal degradation of the fiber core in the composites. Gouadec, Gwenael and Colomban, Philippe and Bansal, Narottam P. Glenn Research Center NASA/TM-2000-210349, NAS 1.15:210349, E-12398

Download or read book Effect of Fiber Reinforcements on Thermo Oxidative Stability and Mechanical Properties of Polymer Matrix Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-02 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: A number of studies have investigated the thermo-oxidative behavior of polymer matrix composites. Two significant observations have been made from these research efforts: (1) fiber reinforcement has a significant effect on composite thermal stability; and (2) geometric effects must be considered when evaluating thermal aging data. A compilation of some results from these studies is presented, and this information shows the influence of the reinforcement fibers on the oxidative degradation of various polymer matrix composites. The polyimide PMR-15 was the matrix material that was used in these studies. The control composite material was reinforced with Celion 6000 graphite fiber. T-40R graphite fibers, along with some very stable ceramic fibers were selected as reinforcing fibers because of their high thermal stability. The ceramic fibers were Nicalon (silicon carbide) and Nextel 312 (alumina-silica-boron oxide). The mechanical properties of the two graphite fiber composites were significantly different, probably owing to variations in interfacial bonding between the fibers and the polyimide matrix. The Celion 6000/PMR-15 bond is very tight but the T-40/PMR-15 bond is less tight. Three oxidation mechanisms were observed: (1) the preferential oxidation of the Celion 6000 fiber ends at cut surfaces, leaving a surface of matrix material with holes where the fiber ends were originally situated; (2) preferential oxidation of the composite matrix; and (3) interfacial degradation by oxidation. The latter two mechanisms were also observed on fiber end cut surfaces. The fiber and interface attacks appeared to initiate interfiber cracking along these surfaces. Bowles, Kenneth J. Glenn Research Center RTOP 505-01-01...

Download or read book Oxidation of Continuous Carbon Fibers Within a Silicon Carbide Matrix Under Stressed and Unstressed Conditions written by Michael C. Halbig and published by . This book was released on 2000 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon fiber reinforced silicon carbide matrix composites (C/SiC) are a ceramic matrix composite (CMC) material that offers benefits for use in a wide range of high temperature structural applications. However the susceptibility of the carbon fibers to degradation in oxidizing environments has hindered the material's use in certain applications requiring long lives under oxidizing conditions. The susceptibility of carbon fibers to oxidation will be discussed as well as the enhancement (improvement in oxidation resistance) of C/SiC materials. Thermogravimetric analysis of carbon fibers shows susceptibility to oxidation in two distinct kinetic regimes. However, in the thermogravimetric (wt. loss) analysis of unstressed, unenhanced, seal coated C/SiC coupons, the two regimes were not observed due to crack closure and matrix effects, which inhibited the oxidation process. Stressed oxidation (creep rupture) tests put the material under a stress, which is a more realistic condition for many applications. In stressed oxidation tests, the two oxidation kinetics regimes were observed. These tests can provide better insight into how the material will perform in applications involving stress. Stressed oxidation of enhanced materials containing oxidation inhibitors showed significantly improved lives at the specific test conditions considered, although there was susceptibility to oxidation at intermediate temperatures.

Download or read book Heat Treatment Effects on Microstructure of SiC Fiber Preforms written by and published by . This book was released on 1999 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Preforms of BN/SiC coated Sylramic SiC fibers were heat treated at 1420 deg, 1600 deg, and 1800 deg C in 0.1 MPa argon or at 1800 deg C in 103 MPa nitrogen for 1 h. Optical, SEM, and TEM techniques were used to analyze the effects of environmental exposure on constituent microstructure of the preforms. TEM analysis of the as-received preforms indicates that the CVI BN coating is predominantly amorphous with small amounts of microcrystalline BN grains, and that the SiC coating on top of the BN coating and SiC fibers is polycrystalline. With increasing temperature of exposure from 1420 deg to 1800 deg C, the preforms heat treated in argon showed increasing amounts of crystalline BN in the CVI BN coating, and coarsening of SiC grains in the CVI SiC coating and SiC fibers. On the other hand, the preforms heal treated in 103 MPa nitrogen at 1800 deg C for 1 h showed microstructural changes inside the fiber tows similar to those heat treated at 1800 deg C in 0.1 MPa argon for 1 h, but the same preforms on the outer periphery of the tows showed reaction between nitrogen and the CVI SiC coating to form Si3N4.

Download or read book Mechanical Chemical and Microstructural Characterization of Monazite Coated Silicon Carbide Fibers written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-15 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tensile strengths of as-received Hi-Nicalon and Sylramic fibers and those having monazite surface coatings, deposited by atmospheric pressure chemical vapor deposition, were measured at room temperature and the Weibull statistical parameters determined. The average tensile strengths of uncoated Hi-Nicalon and Sylramic fibers were 3.19 +/- 0.73 and 2.78 +/- 0.53 GPa with a Weibull modulus of 5.41 and 5.52, respectively. The monazite-coated Hi-Nicalon and Sylramic fibers showed strength loss of approx. 10 and 15 percent, respectively, compared with the as-received fibers. The elemental compositions of the fibers and the coatings were analyzed using scanning Auger microprobe and energy dispersive X-ray spectroscopy. The LaPO4 coating on Hi-Nicalon fibers was approximately stoichiometric and about 50 nm thick. The coating on the Sylramic fibers extended to a depth of about 100 to 150 nm. The coating may have been stoichiometric LaPO4 in the first 30 to 40 nm of the layer. However, the surface roughness of Sylramic fiber made this profile somewhat difficult to interpret. Microstructural analyses of the fibers and the coatings were done by scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. Hi-Nicalon fiber consists of fine beta-SiC nanocrystals ranging in size from 1 to 30 mn embedded in an amorphous matrix. Sylramic is a polycrystalline stoichiometric silicon carbide fiber consisting of submicron beta-SiC crystallites ranging from 100 to 300 nm. Small amount of TiB2 nanocrystallites (approx. 50 nm) are also present. The LaPO4 coating on Hi-Nicalon fibers consisted of a chain of peanut shape particles having monazite-(La) structure. The coating on Sylramic fibers consisted of two layers. The inner layer was a chain of peanut shape particles having monazite-(La) structure. The outer layer was comprised of much smaller particles with a microcrystalline structure. Bansal, N. P. and Wheeler, D. R. and Chen, Y. L. Glenn Rese

Download or read book Silicon Effects on Properties of Melt Infiltrated Sic Sic Composites written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-25 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicon effects on tensile and creep properties, and thermal conductivity of Hi-Nicalon SiC/SiC composites have been investigated. The composites consist of 8 layers of 5HS 2-D woven preforms of BN/SiC coated Hi-Nicalon fiber mats and a silicon matrix, or a mixture of silicon matrix and SiC particles. The Hi-Nicalon SiC/silicon and Hi-Nicalon SiC/SiC composites contained about 24 and 13 vol% silicon, respectively. Results indicate residual silicon up to 24 vol% has no significant effect on creep and thermal conductivity, but does decrease the primary elastic modulus and stress corresponding to deviation from linear stress-strain behavior. Bhatt, Ramakrishna T. and Gyekenyesi, John Z. and Hurst, Janet B. Glenn Research Center NASA/TM-2000-210034, E-12231, NAS 1.15:210034

Download or read book High Temperature Tensile Properties of Unidirectional Hi Nicalon Celsian Composites in Air written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-15 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: High temperature tensile properties of unidirectional BN/SiC-coated Hi-Nicalon SiC fiber reinforced celsian matrix composites have been measured from room temperature to 1200 C (2190 F) in air. Young's modulus, the first matrix cracking stress, and the ultimate strength decreased from room temperature to 1200 C (2190 F). The applicability of various micromechanical models, in predicting room temperature values of various mechanical properties for this CMC, has also been investigated. The simple rule of mixtures produced an accurate estimate of the primary composite modulus. The first matrix cracking stress estimated from ACK theory was in good agreement with the experimental value. The modified fiber bundle failure theory of Evans gave a good estimate of the ultimate strength. Gyekenyesi, John Z. and Bansal, Narottam P. Glenn Research Center NASA/TM-2000-210214, NAS 1.15:210214, E-12333

Download or read book Evaluation of Silicon Carbide Fiber Titanium Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-26 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Izod impact, tensile, and modulus of elasticity were determined for silicon carbide fiber/titanium composites to evaluate their potential usefulness as substitutes for titanium alloys or stainless steel in stiffness critical applications for aircraft turbine engines. Variations in processing conditions and matrix ductility were examined to produce composites having good impact strength in both the as-fabricated condition and after air exposure at elevated temperature. The impact strengths of composites containing 36 volume percent silicon carbide (SiC) fiber in an unalloyed (A-40) titanium matrix were found to be equal to unreinforced titanium-6 aluminum-4 vanadium alloy; the tensile strengths of the composites were marginally better than the unreinforced unalloyed (A-70) matrix at elevated temperature, though not at room temperature. At room temperature the modulus of elasticity of the composites was 48 percent higher than titanium or its alloys and 40 percent higher than that of stainless steel. Jech, R. W. and Signorelli, R. A. Glenn Research Center NASA-TM-79232, E-134

Download or read book Oxidation Effects on the Mechanical Properties of SiC Fiber Reinforced Reaction bonded Silicon Nitride Matrix Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-09 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: The room temperature mechanical properties of SiC fiber reinforced reaction bonded silicon nitride composites were measured after 100 hrs exposure at temperatures to 1400 C in nitrogen and oxygen environments. The composites consisted of approx. 30 vol percent uniaxially aligned 142 micron diameter SiC fibers in a reaction bonded Si3N4 matrix. The results indicate that composites heat treated in a nitrogen environment at temperatures to 1400 C showed deformation and fracture behavior equivalent to that of the as-fabricated composites. Also, the composites heat treated in an oxidizing environment beyond 400 C yielded significantly lower tensile strength values. Specifically in the temperature range from 600 to 1000 C, composites retained approx. 40 percent of their as-fabricated strength, and those heat treated in the temperatures from 1200 to 1400 C retained 70 percent. Nonetheless, for all oxygen heat treatment conditions, composite specimens displayed strain capability beyond the matrix fracture stress; a typical behavior of a tough composite. Bhatt, Ramakrishna T. Glenn Research Center RTOP 510-01-0A...

Download or read book Fiber Volume Fraction Effects on Fatigue Response of a SCS 6 Ti 15 3 Metal Matrix Composite at Elevated Temperature written by Sean C. Coghlan and published by . This book was released on 1997-09-01 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study was to determine the effects of fiber volume fraction on the fatigue behavior of Silicon Carbide fiber-reinforced Titanium alloy, SCS-6/Ti-15-3. Three fiber volume fractions were investigated; 15%, 25%, and 42%. The tests were performed under fully-reversed, strain- controlled conditions at 427 C. The primary objectives of this study were to develop a fatigue life diagram and to document the damage and failure mechanisms. Compressive loads on the slender specimens were kept from buckling the specimens through the use of a buckling guide. This device allows unrestricted axial movement of the composite, while preventing any out-of-plane motion. No buckling damage due to compression was found in any of the specimens. Modulus behavior and stress versus strain curves were recorded during cycling for each test. An applied strain range between 0.5% and 1.1% was used for the majority of the tests. This resulted in fatigue lives between approximately 10, 000 and 100,000 cycles. The resulting fatigue life diagram showed similar life at strain ranges at and above 0.008 mm/mm for all fiber volume fractions. At strain levels below 0.008 mm/mm, there was an increasing fatigue life with increasing fiber volume fraction. The 15% and 42% V sub f material was consolidated with a molybdenum cross-weave to hold the fibers in alignment. The 25% V sub f material had a titanium-niobium cross-weave for the same purpose. The Mo cross-weave was present on every fracture surface of the 15% and 42% V sub f material. This indicated that it was detrimental to the fatigue life of the composite. No cross-weave material was found on the fracture surfaces of the 25% V sub f. Major cause of specimen failure was the initiation and propagation of fatigue cracks in the matrix that were perpendicular to the applied load.

Download or read book High Temperature Ceramic Matrix Composites written by Walter Krenkel and published by Wiley-VCH. This book was released on 2001 with total page 1044 pages. Available in PDF, EPUB and Kindle. Book excerpt: The extreme high temperature stability and damage tolerance of materials and components required for space, terrestrial, energetic and many other applications can only be achieved by ceramic materials. All over the world research is going on to develop ceramics with quasiductile behaviour. The materials with the highest potential for high temperature applications are fibre reinforced ceramic matrix composites (CMC). The international conference HT-CMC 4 in Munich will continue the tradition of its successful predecessor meetings held in Bordeaux (France, 1993), Santa Barbara (USA, 1995) and Osaka (Japan, 1998). This conference series has been recognized as the central meeting event in high temperature CMC science and technology and demonstrates the great interest in research and development on reinforced ceramics. The Proceedings of this conference will therefore be a valuable reference for every materials scientist or engineer involved in this field of high-tech materials development.

Download or read book Mechanical Behavior of a Continuous Fiber Reinforced Aluminum Matrix Composite Subjected to Transverse and Thermal Loading written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-10-21 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: The transverse properties of an aluminum alloy metal matrix composite reinforced by continuous alumina fibers were investigated. The composite is subjected to both mechanical and cyclic thermal loading. The results of an experimental program indicate that the shakedown concept of structural mechanics provides a means of describing the material behavior. When the loading conditions are within the shakedown region, the material finally responds in an elastic manner after initial plastic response, and for loading conditions outside the shakedown region, the material exhibits a rapid incremental plastic strain accumulation. The failure strain varies by an order of magnitude according to the operating conditions. Hence, for high mechanical and low thermal loading, the failure strains is small; for low mechanical and high thermal loading, the failure strain is large. Jansson, S. and Leckie, F. A. Unspecified Center NAG3-894; RTOP 510-01-50...

Download or read book Creep Behavior of Tungsten Fiber Reinforced Niobium Metal Matrix Composites written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-16 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tungsten fiber reinforced niobium metal matrix composites were evaluated for use in space nuclear power conversion systems. The composite panels were fabricated using the arc-spray monotape technique at the NASA Lewis Research Center. The creep behavior of W/Nb composite material was determined at 1400 and 1500 K in vacuum over a wide range of applied loads. The time to reach 1 percent strain, the time to rupture, and the minimum creep rate were measured. The W/Nb composites exceeded the properties of monolithic niobium alloys significantly even when compared on a strength to density basis. The effect of fiber orientation on the creep strength also was evaluated. Kirkendall void formation was observed at the fiber/matrix interface; the void distribution differed depending on the fiber orientation relative to the stress axis. A relationship was found between the fiber orientation and the creep strength. Grobstein, T. L. Glenn Research Center NASA-TM-102307, E-4995, DOE/NASA/16310-11, NAS 1.15:102307 DE-AI03-86SF-16310; RTOP 586-01-11...